Biology subjects

Maier, T. R.

Publications and source records attributed to Maier, T. R..

7 recordsLinked to original sources

bioRxiv2025

Genome reannotation and effector candidate identification in Meloidogyne chitwoodi through gland-specific transcriptome analysis

The root-knot nematode (RKN) Meloidogyne chitwoodi is a threat for potato production in the western United States, negatively impacting potato yield and product value. Meloidogyne chitwoodi produce proteins, called effectors, in their esophageal glands that are secreted during parasitism and play integral roles in plant-nematode interactions. Because the esophageal glands are the main effector secretory organ, we performed juvenile gland isolation and gland transcriptome analysis. The data allowed us to improve the M. chitwoodi genome annotation. Additionally, the gland-specific transcriptome data gave us an enrichment of gland-localized genes, which was validated by in situ hybridization. The gland transcriptome analysis led to the identification of 111 effector candidates. One of the effectors, Mc15g003960, which was highly expressed in the pre-parasitic J2 gland tissue, was further characterized. Expression of Mc15g003960 in Arabidopsis resulted in increased galling by M. chitwoodi. However, the ectopic expression of Mc15g003960 in planta did not suppress defense-related callose deposition, suggesting that this effector might be involved in processes other than interfering with plant basal defense responses. Our data shows that using the gland transcriptome, good quality genome annotation and stringent criteria, we can increase the efficiency of effector identification, which can be used to develop more sustainable management tools. Authors summaryThe root-knot nematode Meloidogyne chitwoodi is a major problem for potato farmers in the western U.S., reducing crop yield and quality. These nematodes produce special proteins, called effectors, in their esophageal glands, which help them infect plants. Since these glands are the main source of effectors, we isolated them from juvenile nematodes and analyzed their gene expression. This helped us improve the nematodes genome map and identify genes specific to the glands. From this study, we found 111 potential effector genes. One of them, Mc15g003960, was highly active before the nematode started feeding. When we introduced this gene into Arabidopsis plants, the nematodes caused more damage, but it didnt seem to weaken the plants basic defense system. This suggests Mc15g003960 is not suppressing plant defenses and has a different role in helping the nematode with successful infection. Overall, our approach helped us identify key effectors more efficiently, which could lead to better ways to manage nematode infestations in the future.

molecular biology↗

bioRxiv2024

Nemacounter: A user-friendly software to accurately phenotype SCN cysts

The soybean-cyst nematode (SCN; Heterodera glycines) is one of the most destructive pests affecting soybean crops. Effective management of SCN is imperative for the sustainability of soybean agriculture. A promising approach to achieving this goal is the development and breeding of new resistant soybean varieties. Researchers and breeders typically employ exploratory methods such as Genome-Wide Association Studies or Quantitative Trait Loci mapping to identify genes linked to resistance. These methods depend on extensive phenotypic screening. The primary phenotypic measure for assessing SCN resistance is often the number of cysts that form on a plants root system. Manual counting hundreds of cysts on a given root system is not only laborious but also subject to variability due to individual assessor differences. Additionally, while measuring cyst size could provide valuable insights due to its correlation with cyst development, this aspect is frequently overlooked because it demands even more hands-on work. To address these challenges, we have created Nemacounter, an intuitive software designed to detect, count, and measure the size of cysts autonomously. Nemacounter boasts a user-friendly graphical interface, simplifying the process for users to obtain reliable results. It enhances productivity by delivering annotated images and compiling data into csv files for easy analysis and reporting.

plant biology↗

bioRxiv2024

The SUbventral-Gland master Regulator (SUGR) of nematode virulence

All pathogens must tailor their gene expression to their environment. Therefore, targeting host:parasite biology that regulates these changes in gene expression could open up routes to pathogen control. Here, we show that in the plant-parasitic nematode Heterodera schachtii, host signals (termed effectostimulins) within plant roots activate the master regulator sugr1. SUGR1, then, directly binds effector promoters, and orchestrates their production. Effector production, in turn, facilitates host entry, releasing more effectostimulins. These data show that gene expression during the very earliest stages of parasitism is defined by a feed forward loop for host entry. Importantly, we demonstrate that blocking SUGR1 blocks parasitism, underlining the SUGR1 signalling cascade as a valuable target for crop protection. Given that nematodes also parasitise humans and other animals, the potential impact is broad: disrupting effector production could, in principle, be applied to any pathogen that secrets effectors. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=146 SRC="FIGDIR/small/576598v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@cebedaorg.highwire.dtl.DTLVardef@153fe87org.highwire.dtl.DTLVardef@16b6957org.highwire.dtl.DTLVardef@d0e920_HPS_FORMAT_FIGEXP M_FIG C_FIG

pathology↗

bioRxiv2021

The genome and lifestage-specific transcriptomes of a plant-parasitic nematode and its host reveal susceptibility genes involved in trans-kingdom synthesis of vitamin B.

Plant-parasitic nematodes are a major, and in some cases a dominant, threat to crop production in all agricultural systems. The relative scarcity of classical resistance genes highlights a pressing need to identify new ways to develop nematode-resistant germplasm. Here, we sequence and assemble a high-quality genome of the model cyst nematode Heterodera schachtii to provide a platform for the first system-wide dual analysis of host and parasite gene expression over time, covering all major stages of the interaction. This novel approach enabled the analysis of the hologenome of the infection site, to identify metabolic pathways that were incomplete in the parasite but complemented by the host. Using a combination of bioinformatic, genetic, and biochemical approaches, we show that the highly atypical completion of vitamin B5 biosynthesis by the parasitic animal, putatively enabled by a horizontal gene transfer from a bacterium, is critically important for parasitism. Knockout of either the plant-encoded or the now nematode-encoded steps in the pathway blocks parasitism. Our experiments establish a reference for cyst nematodes, use this platform to further our fundamental understanding of the evolution of plant-parasitism by nematodes, and show that understanding congruent differential expression of metabolic pathways represents a new way to find nematode susceptibility genes, and thereby, targets for future genome editing-mediated generation of nematode-resistant crops.

genetics↗

bioRxiv2020

Towards genetic modification of plant-parasitic nematodes: delivery of macromolecules to adults and expression of exogenous mRNA in second stage juveniles.

Plant-parasitic nematodes are a continuing threat to food security, causing an estimated 100 billion USD in crop losses each year. The most problematic are the obligate sedentary endoparasites (primarily root knot nematodes and cyst nematodes). Progress in understanding their biology is held back by a lack of tools for functional genetics: forward genetics is largely restricted to studies of natural variation in populations, and reverse genetics is entirely reliant on RNA interference. There is an expectation that the development of functional genetic tools would accelerate the progress of research on plant-parasitic nematodes, and hence the development of novel control solutions. Here, we develop some of the foundational biology required to deliver a functional genetic tool kit in plant-parasitic nematodes. We characterise the gonads of male Heterodera schachtii and Meloidogyne hapla in the context of spermatogenesis. We test and optimise various methods for the delivery, expression, and/or detection of exogenous nucleic acids in plant-parasitic nematodes. We demonstrate that delivery of macromolecules to cyst and root knot nematode male germlines is difficult, but possible. Similarly, we demonstrate the delivery of oligonucleotides to root knot nematode gametes. Finally, we develop a transient expression system in plant-parasitic nematodes by demonstrating the delivery and expression of exogenous mRNA encoding various reporter genes throughout the body of H. schachtii juveniles using lipofectamine-based transfection. We anticipate these developments to be independently useful, will expedite the development of genetic modification tools for plant-parasitic nematodes, and ultimately catalyze research on a group of nematodes that threaten global food security.

genetics↗

bioRxiv2020

Low ribosomal RNA genes copy number provoke genomic instability and chromosomal segment duplication events that modify global gene expression and plant-pathogen response

Among the hundreds of ribosomal RNA (rRNA) gene copies organized as tandem repeats in the nucleolus organizer regions (NORs), only a portion is usually actively expressed in the nucleolus and participate in the ribosome biogenesis process. The role of these extra-copies remains elusive, but previous studies suggested their importance in genome stability and global gene expression. Because the nucleolus is also a platform for nuclear organization, we tested the impact of a decreased amount of rRNA gene copies on the Arabidopsis thaliana 3D genome organization and stability, using an A. thaliana line only containing 20% of rRNA gene copies (20rDNA line). Compared to the wild-type Col-0, the 20rDNA line shows several signs of genomic instability, such as variations in 3D genome organization, spontaneous double-strand breaks accumulation, transcriptomic changes, and higher DNA methylation level. Strikingly, using genomic and microscopic approaches, we identified seven large tandem duplications in direct orientation (TDDOs) ranging from 60 kb to 1.44 Mb. As a consequence, more than 600 genes were duplicated, often associated with an increase in their expression level. Among them, we found several upregulated genes involved in plant-pathogen response, which could explain why the 20rDNA line is hyper-resistant to both bacterial and nematode infections. Finally, we show that the TDDOs create gene fusions and/or truncations and we discuss their potential implications on plant genome evolution.

plant biology↗

bioRxiv2018

The genome of the soybean cyst nematode (Heterodera glycines) reveals complex patterns of duplications involved in the evolution of parasitism genes

Heterodera glycines, commonly referred to as the soybean cyst nematode (SCN), is an obligatory and sedentary plant parasite that causes over a billion-dollar yield loss to soybean production annually. Although there are genetic determinants that render soybean plants resistant to certain nematode genotypes, resistant soybean cultivars are increasingly ineffective because their multi-year usage has selected for virulent H. glycines populations. The parasitic success of H. glycines relies on the comprehensive re-engineering of an infection site into a syncytium, as well as the long-term suppression of host defense to ensure syncytial viability. At the forefront of these complex molecular interactions are effectors, the proteins secreted by H. glycines into host root tissues. The mechanisms of effector acquisition, diversification, and selection need to be understood before effective control strategies can be developed, but the lack of an annotated genome has been a major roadblock. Here, we use PacBio long-read technology to assemble a H. glycines genome of 738 contigs into 123Mb with annotations for 29,769 genes. The genome contains significant numbers of repeats (34%), tandem duplicates (18.7Mb), and horizontal gene transfer events (151 genes). Using previously published effector sequences, the newly generated H. glycines genome, and comparisons to other nematode genomes, we investigate the evolutionary mechanisms responsible for the emergence and diversification of effector genes.

genomics↗